Koko, the world's most famous gorilla, is a cat lover. Whatever you think
of her abilities to communicate via sign language, there's no doubting that
she treasured her tailless kitten All Ball. Sadly, All Ball died after being
hit by a car; when the news of Koko's mourning broke, as
TIME noted a few months later, "Hearts broke across America." The 1985
write-up went on to report that Koko had received a new kitty and signed "My
cat good." Psychologist Francine "Penny" Patterson, who began teaching Koko
sign language in the 1970s, published the book Koko's Kitten in 1987.